The present invention is related generally to aerosol sampling devices, and specifically to an aerosol sampler inlet in the form of a cyclone fractionator adapted for accurate, omni-directional air sampling of particulate substances in the air.
It is recognized and generally accepted that chemical air pollution is deleterious to the health of persons. Scientists are becoming aware that particulate pollution in air also has adverse effects on the health of persons. The U.S. Environmental Protection Agency has set present standards for particulate matter in air in terms of mass per unit volume limits over a preselected period of time. For example, present standards for particulate matter are 75 micrograms per cubic meter average annular limit (geometric mean) and 260 micrograms per cubic meter in 24 hours (geometric mean) for particles larger than 45 microns.
New data have recently become available which indicate that protection of public health may be served better by considering only inhalable particles. The International Standards Organization has proposed a standard based upon particles deposited on the tracheo-bronchial and alveolar regions of the human respiratory tract. This proposal is now referred to as thoracic deposition or TPC (Thoracic Particles). The Clear Air Scientific Advisory Committee (CASAC) has now recommended to the United States Environmental Protection Agency that a 10 micron particle size range be used as the new primary standard for average annual limits and 24 hour limits of micrograms per cubic meter clean air standards. Therefore, a need exists to develop monitoring instruments that mimic the deposition of particles in the thoracic region of the human respiratory system.
An ideal inlet for assessing the true ambient particulate concentration is defined by a log-normal effectiveness curve having a D.sub.50 equal to 10 microns and a unity slope, where D.sub.50 is defined as the particle size associated with a sampling effectiveness of 50 percent. This ideal inlet is that which has the performance specification of sampling 100% of the available ambient airborne particulate mass. Effectiveness is defined as the ratio of mass deposited on the collection substrate of the sampler to the total airborne mass approaching the inlet and with the proper corrections made for sampling volumes. Such an ideal inlet could also be defined as one in which performance characteristics allow collection of an accurate mass representative sample of the TP fraction independent of the sampling conditions of wind speed and direction. Prior to this invention, no such sampling devices were available.